http://http://ir.library.oregonstate.edu:80/xmlui The ScholarsArchive@OSU digital repository system captures, stores, indexes, preserves, and distributes digital research material. 2013-05-22T20:56:22Z http://hdl.handle.net/1957/38709 Linearizing techniques for voltage controlled oscillator based analog to digital converters Rao, Sachin B. Voltage controlled oscillator (VCO) based ADC is an important class of time-domain ADC that has gained widespread acceptance due to their several desirable properties. VCO-based ADCs behave like an open-loop continuous time ΔΣ modulator and achieve excellent resolution by first order noise shaping the quantization error. However, the SNDR of an open-loop VCO-based ADC is severely distortion limited by the voltage-to-frequency tuning characteristics of the VCO. This work examines various techniques that have already been proposed to overcome the VCO tuning non-linearity problem. Two new VCO-based ADC architectures, that overcome the limitations of the conventional approaches, are proposed. In the first approach, the ADC is linearized by forcing the VCO to operate at only two operating points using a front-end two level modulator. With this technique, the linearity is improved without using either a multi-bit feedback DAC or calibration. Fabricated in a 90 nm CMOS process, the prototype ADC achieves better than 71 dB SFDR and 59.1 dB SNDR in 8 MHz signal bandwidth while consuming 4.3 mW power. The ADC achieves a figure of merit of 366 fJ/conv-step, which is comparable with other state of the art time based ADCs. In the second approach, the need for a front-end two level modulator is obviated using linearizers, which introduce an inverse of VCO’s voltage to frequency characteristics in the signal path. A deterministic digital calibration unit runs continuously in the background and builds the inverse voltage to frequency transfer function. Implemented in a 90nm CMOS process, this on-chip calibration improves SFDR of the prototype ADC from 46 dB to more than 83 dB. The ADC consumes 4.1 mW power and achieves 73.9 dB SNDR in 5 MHz signal bandwidth resulting in an excellent figure of merit of 101 fJ/conv-step. Graduation date: 2013; Access restricted to the OSU Community at author's request from May 22, 2013 - May 22, 2015 2013-05-13T00:00:00Z http://hdl.handle.net/1957/38708 Intraperitoneal implantation of life-long telemetry transmitters in otariids Horning, Markus; Haulena, Martin; Tuomi, Pamela A; Mellish, Jo-Ann E. Background: Pinnipeds, including many endangered and declining species, are inaccessible and difficult to monitor for extended periods using externally attached telemetry devices that are shed during the annual molt. Archival satellite transmitters were implanted intraperitoneally into four rehabilitated California sea lions (Zalophus californianus) and 15 wild juvenile Steller sea lions (Eumetopias jubatus) to determine the viability of this surgical technique for the deployment of long-term telemetry devices in otariids. The life history transmitters record information throughout the life of the host and transmit data to orbiting satellites after extrusion following death of the host. Results: Surgeries were performed under isoflurane anesthesia and single (n = 4) or dual (n = 15) transmitters were inserted into the ventrocaudal abdominal cavity via an 8.5 to 12 cm incision along the ventral midline between the umbilicus and pubic symphysis or preputial opening. Surgeries lasted 90 minutes (SD = 8) for the 19 sea lions. All animals recovered well and were released into the wild after extended monitoring periods from 27 to 69 days at two captive animal facilities. Minimum post-implant survival was determined via post-release tracking using externally attached satellite transmitters or via opportunistic re-sighting for mean durations of 73.7 days (SE = 9.0, Z. californianus) and 223.6 days (SE = 71.5, E. jubatus). Conclusion: The low morbidity and zero mortality encountered during captive observation and post-release tracking periods confirm the viability of this surgical technique for the implantation of long-term telemetry devices in otariids. This is the publisher’s final pdf. The published article is copyrighted by BioMed Central Ltd. and can be found at: http://www.biomedcentral.com/bmcvetres/. 2008-12-10T00:00:00Z http://hdl.handle.net/1957/38707 Carbon Stocks of Tropical Coastal Wetlands within the Karstic Landscape of the Mexican Caribbean Kauffman, J. Boone; Medina, Israel; Gamboa, Julieta N.; Torres, Olmo; Caamal, Juan P.; Reza, Miriam; Herrera-Silveira, Jorge A.; Adame, Maria Fernanda Coastal wetlands can have exceptionally large carbon (C) stocks and their protection and restoration would constitute an effective mitigation strategy to climate change. Inclusion of coastal ecosystems in mitigation strategies requires quantification of carbon stocks in order to calculate emissions or sequestration through time. In this study, we quantified the ecosystem C stocks of coastal wetlands of the Sian Ka'an Biosphere Reserve (SKBR) in the Yucatan Peninsula, Mexico. We stratified the SKBR into different vegetation types (tall, medium and dwarf mangroves, and marshes), and examined relationships of environmental variables with C stocks. At nine sites within SKBR, we quantified ecosystem C stocks through measurement of above and belowground biomass, downed wood, and soil C. Additionally, we measured nitrogen (N) and phosphorus (P) from the soil and interstitial salinity. Tall mangroves had the highest C stocks (987 ± 338 Mg ha⁻¹) followed by medium mangroves (623 ± 41 Mg ha⁻¹), dwarf mangroves (381 ± 52 Mg ha⁻¹) and marshes (177 ±73 Mg ha⁻¹). At all sites, soil C comprised the majority of the ecosystem C stocks (78-99%). Highest C stocks were measured in soils that were relatively low in salinity, high in P and low in N: P, suggesting that P limits C sequestration and accumulation potential. In this karstic area, coastal wetlands, especially mangroves, are important C stocks. At the landscape scale, the coastal wetlands of Sian Ka'an covering approximate to ≈172,176 ha may store 43.2 to 58.0 million Mg of C. This is the publisher’s final pdf. The published article is copyrighted by Public Library of Science and can be found at: http://www.plos.org/. 2013-02-14T00:00:00Z http://hdl.handle.net/1957/38706 Proteins Secreted via the Type II Secretion System: Smart Strategies of Vibrio cholerae to Maintain Fitness in Different Ecological Niches Sikora, Aleksandra E. No abstract available. This is the publisher’s final pdf. The published article is copyrighted by Public Library of Science and can be found at: http://www.plos.org/. 2013-02-21T00:00:00Z